Storage media for computers and other types of electronic devices generally come in two types: volatile memory and non-volatile memory. Volatile memory loses its contents when power is no longer being supplied to the memory, whereas non-volatile memory maintains its contents even when power is not being supplied to the memory. The most common type of volatile memory is random-access memory (RAM), which is most commonly available as and implemented as an integrated circuit (IC). The term data storage medium is used herein in a broad sense, and encompasses IC memory, as well as other types of data storage media.
By comparison, non-volatile memory has perhaps more commonly been available as and implemented as magnetic and optical media, including hard disk drives, floppy disks, compact disc read-only memories (CD-ROM's), CD re-writable (CD-RW) discs, and digital versatile discs (DVD's), among others. Historically, non-volatile memory implemented as an IC was primarily available as ROM that was not re-recordable, such as hard-wired ROM and programmable ROM (PROM). More recently, IC non-volatile memory has become available as various types of flash memory, which is more technically known as electrically erasable PROM (EEPROM).
IC-based data storage media is typically read from and, where applicable, written to, using electric signals. By comparison, magnetic and optical data storage media is typically read from, and where applicable, written to, using magnetic sensors and optical sensors, where the latter usually include some type of illuminating beam. However, a new type of data storage medium has been contemplated that can be implemented as an IC, but that is read from and written to using an illuminating beam. A phase-changeable layer is present that can be switched between two different phases by being subjected to the illuminating beam. The two phases correspond to different logical values, such as binary one and binary zero.
For reading the logical value stored in the phase-changeable layer, the medium is subjected to the illuminating beam at a low intensity. This induces current within the medium, which is then detected and correlated with the current phase of the re-recordable storage medium to determine the logical value stored in the medium. However, current may potentially leak from one memory cell of the medium to another, causing errors.
For writing a logical value to the phase-changeable layer, the medium is subjected to the illuminating beam at a high intensity. This causes the phase-changeable layer to switch from one phase to the other phase. However, the power needed to change the phase potentially may be relatively large, making the medium less desirable for environments in which power is a scarce resource.
For these and other reasons, there is a need for the present invention.